1. Technical Field
The invention relates to mobile communications and, more particularly, to better supporting communication with mobile devices relating to multimedia broadcast multicast service (MBMS).
2. Discussion of Related Art
Abbreviations
    3GPP Third generation partnership program    BCCH Broadcast Control CHannel    CN Core Network    eNB eNodeB    eNodeB E-UTRAN Node B    EPC Evolved Packet Core    E- Enhanced-UTRAN    UTRAN    LTE Long Term Evolution    MCCH MBMS Control Channel    MME Mobility Management Entity    MBMS Multimedia Broadcast Multicast Service    RACH Random Access CHannel    RAN Radio Access Network    RRC Radio Resource Control    SAE System Architecture Evolution    SFN System Frame Number    UL Uplink    UMTS Universal Mobile Telecommunications System    UTRAN Universal Terrestrial Radio Access Network
The following appears in numbered section 2 of the 3GPP document R3-070395 (Joint meeting of 3GPP TSG RAN2, RAN3, SA2 12-16 Feb. 2007, St. Louis, Mo., USA):                “2. LTE/SAE Working Assumption for MBMS        1) No UE Subscription verification is performed by the eNodeB or EPC for MBMS sessions/services and therefore no UE context information is required to be propagated to the eNodeB from the CN.        2) MBMS Services in LTE/SAE can be in one of two modes:        a. MBMS Broadcast mode—MBMS services sent in this mode are transmitted everywhere within the MBMS Service Area by the network irrespective of UE location or quantity. The UEs receiving MBMS in this mode do not need to leave RRC Idle for MBMS reception.        b. MBMS Enhanced Broadcast mode—MBMS services sent in this mode are not transmitted everywhere and UE location and quantity may be taken into account by the network. The UEs receiving LTE MBMS may need to leave RRC Idle state for MBMS reception.        No MBMS context is required to be established by the UE in any node above the eNodeB in LTE/SAE, for either MBMS Broadcast or MBMS Enhanced Broadcast mode.”        
It has been agreed in 3GPP that UE in LTE_IDLE or even RRC_IDLE state can receive MBMS services. Network awareness about UEs which are using or have used MBMS services, however, is beneficial for the system operation and performance. This has been justified in LTE requirements of MBMS counting and audience-measurement. The direct applications of the MBMS counting and audience-measurement results are to select and configure efficient MBMS transmission mode, SFN area and transmission parameters in a possibly adaptive fashion.
The need for such awareness can go deeper. For instance, it could also be motivated by the objectives described by the ARENA (Audience measurement Research Extended to New convergent media Applications and services) project (reference FP6-027124 with start date 1 Jan. 2006 and end date 31 Dec. 2006) which seeks to develop a model for covering audience measurement irrespective of the underlying delivery method or access technologies. Such a development might include identification of metrics needed such as metrics for classifying audiences and media content, identifying audience share, reach, loyalty, demographics, viewing and navigation patterns, etc.
Audience measurement for MBMS in L3G LTE has been discussed for instance in R2-071468. FIG. 2 thereof shows the eNB sending a Counting Indication message to a UE and receiving a Counting Response message in reply. However, the UE must be in RRC_Connected state to send a Counting Response. In this scenario, if UE in RRC_Idle state it has to perform an RACH procedure and complete an RRC_connection_establishment in between the receipt of the Counting Indication message from the eNB and the sending of the Counting Response from the eNB. This is rather burdensome from the UE's point of view and will moreover use up some of the air interface resources.
In 3G LTE there is a lack of simple and effective mechanisms to gain such awareness about IDLE UEs which are receiving or have just received MBMS services in which explicit counting is prevented or not required.